This invention relates to personal computer systems and in particular to an apparatus and method for loading BIOS into a personal computer system from a remote storage location.
Personal computer systems in general and IBM personal computers in particular have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER AT and IBM's PERSONAL SYSTEM/2 Models 25, 30, 50, 50Z, 55SX, 60, 65SX, 70 and 80.
These systems can be classified into two general families. The first family, usually referred to as Family I, uses a bus architecture exemplified by the IBM PERSONAL COMPUTER AT and other "IBM compatible" machines. The second family, referred to as Family II, uses IBM's MICROCHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 80. MICROCHANNEL and PERSONAL SYBTEM/2 are trademarks of International Business Machines Corporation.
Beginning with the earliest personal computer system of the Family I models, such as the IBM Personal Computer, it was recognized that software compatibility would be of utmost importance. In order to achieve this goal, an insulation layer of system resident code, also called "microcode", was established between the hardware and software. This code provided an operational interface between a user's application program/operating system to relieve the user of the concern about the characteristics of hardware devices. Eventually, the code developed into a Basic Input/Output System (BIOS), for allowing new devices to be added to the system, while insulating the application program from the peculiarities of the hardware. The importance of BIOS was immediately evident because it freed a device driver from depending on specific device hardware characteristics while providing the device driver with an intermediate interface to the device. Since BIOS was an integral part of the system and controlled the movement of data in and out of the system processor, it was resident on the system planar and was shipped to the user in non-volatile read only memory (ROM). For example, BIOS in the original IBM Personal Computer occupied 8K of ROM resident on the planar board.
As new models of the personal computer family have been introduced, BIOS has been updated and expanded to include new hardware and I/O devices. As could be expected, BIOS increased in memory size. For example, with the introduction of the IBM PERSONAL COMPUTER AT, BIOS grew to require 32K bytes of ROM.
Today, with the development of new technology, personal computer systems of the Family II models are growing even more sophisticated and are being made available to consumers more frequently. Since the technology is rapidly changing and new I/O devices are being added to the personal computer systems, modification to the BIOS has become a significant problem in the development cycle of the personal computer system.
For instance, with the introduction of the IBM PERSONAL SYSTEM/2 with MICROCHANNEL architecture, a significantly new BIOS, known as advanced BIOS, or ABIOS, was developed. However, to maintain software compatibility, BIOS from the Family I models had to be included in the Family II models. The Family I BIOS became known as Compatibility BIOS or CBIOS. In Family I machines, only 32K bytes of ROM were resident on the planar board for retaining BIOS. Family II systems have been expanded to 96K bytes of ROM. Even with the addition of ABIOS, ABIOS and CBIOS could still squeeze into 96K of ROM. However, only a small percentage of the 96K ROM area remained available for expansion. With the addition of future I/O devices, CBIOS and ABIOS will eventually run out of ROM space. Thus, new I/O technology will not be able to be easily integrated within CBIOS and ABIOS.
Due to these problems, plus a desire to make modifications in Family II BIOS as late as possible in the development cycle, it became appropriate to off load portions of BIOS from the ROM. To accomplish this, portions of BIOS were stored and loaded from a fixed disk. However, it quickly became evident that loading only from a fixed disk had some limitations. Mainly, if the disk became incapacitated, the system was unusable. Also, changes to system configuration would lead to compatibility problems between BIOS and the new system configuration. Therefore, provision has been made for loading BIOS from a direct access storage device other than the resident fixed disk.
In yet another related development, personal computers have been joined together into networks in various ways and through the use of various schemes. In some such networks, personal computers are used essentially as "dumb" terminals communicating with a powerful host computer which may be of the large size known as a mainframe and which serves to provide large databases and as the location of residence of applications programs which will manipulate data. In other network arrangements, personal computers are used as "smart" terminals which obtain application programs and sometimes data from a central file server (which may be another personal computer equipped with a direct access storage device of large capacity and capable of operating at relatively quick data recovery speeds), manipulate or receive entry of data, and return data to the file server. In still other arrangements, a group of personal computers may share among the group resources available to one or more of the systems in the network, such as peripheral devices such as printers, scanners, modems, etc. and application program or data files located on various direct access storage devices each of which is more directly associated with a single one of the resource sharing personal computers. Many such network arrangements are known as a local area network or LAN (the latter acronym being a defined term for purposes of this description).
As the use of personal computers in a LAN has increased, it has been recognized that the expense of a machine used in such an environment can be decreased by removing from such a computer system elements which are more usually found in personal computers as defined hereinabove. As a result, personal computers lacking direct access storage devices have come into use. Such an apparatus has, prior to the present invention, been provided with sufficient non-volatile memory to retain the full BIOS necessary and appropriate for use of the personal computer, such as the 96k of ROM referred to above in the discussion of the BIOS developed for use with Family II machines. However, the cost of providing such memory capability can be avoided, and a more economical machine provided for certain limited types of usage, where the necessity of providing non-volatile memory is more substantially eliminated. Prior to the present invention, there has been no solution which achieved such a result while maintaining the desirable characteristics of a "smart" LAN workstation.
The use of personal computers in local area networks may give rise to yet another area of potential impact in that any given personal computer typically is configured for certain functions which are provided, with such configuring being done at least in part as a BIOS function. With a stand alone personal computer not associated with a LAN, autoconfiguration is known and conventionally occurs as part of a start up procedure. With a computer associated with a LAN, such autoconfiguration may occur as a function of BIOS stored in the computer and accessed as part of the start up procedure. However, it may be desirable for configuration of a particular computer connected with a LAN to be automatically set by the LAN on power on for that computer.